Janus kinases (JAKs) are cytoplasmic tyrosine kinases that transduce cytokine signaling from membrane receptors to STAT transcription factors. Four JAK family members are described, JAK1, JAK2, JAK3 and TYK2. Upon binding of the cytokine to its receptor, JAK family members auto- and/or transphosphorylate each other, followed by phosphorylation of STATs that then migrate to the nucleus to modulate transcription. JAK-STAT intracellular signal transduction serves the interferons, most interleukins, as well as a variety of cytokines and endocrine factors such as EPO, TPO, GH, OSM, LIF, CNTF, GM-CSF and PRL. (Vainchenker et al., 2008)
The combination of genetic models and small molecule JAK inhibitor research revealed the therapeutic potential of several JAKs. JAK3 is validated by mouse and human genetics as an immune-suppression target. (O'Shea et al., 2004) JAK3 inhibitors were successfully taken into clinical development, initially for organ transplant rejection but later also in other immuno-inflammatory indications such as rheumathoid arthritis (RA), psoriasis and Crohn's disease (http://clinicaltrials.gov/).
TYK2 is a potential target for immuno-inflammatory diseases, being validated by human genetics and mouse knock-out studies. (Levy and Loomis, 2007)
JAK1 is a target in the immuno-inflammatory disease area. JAK1 heterodimerizes with the other JAKs to transduce cytokine-driven pro-inflammatory signaling. Therefore, inhibition of JAK1 is of interest for immuno-inflammatory diseases with pathology-associated cytokines that use JAK1 signaling, such as IL-6, IL-4, IL-5, IL-13, or IFNgamma, as well as for other diseases driven by JAK-mediated signal transduction.
The degeneration of cartilage is the hallmark of various diseases, among which rheumatoid arthritis and osteoarthritis are the most prominent. Rheumatoid arthritis (RA) is a chronic joint degenerative disease, characterized by inflammation and destruction of the joint structures. When the disease is unchecked, it leads to substantial disability and pain due to loss of joint functionality and even premature death. The aim of an RA therapy, therefore, is not only to slow down the disease but to attain remission in order to stop the joint destruction. Besides the severity of the disease outcome, the high prevalence of RA (˜0.8% of adults are affected worldwide) means a high socio-economic impact. (Choy and Panayi, 2001; Firestein, 2003; Lee and Weinblatt, 2001; O'Dell, 2004; Smolen and Steiner, 2003).
JAK1 and JAK2 are implicated in intracellular signal transduction for many cytokines and hormones. Pathologies associated with any of these cytokines and hormones can be ameliorated by JAK1 and JAK2 inhibitors. Hence, several allergic or inflammatory conditions and autoimmune diseases might benefit from treatment with compounds described in this invention including rheumatoid arthritis, systemic lupus erythematosis, juvenile idiopathic arthritis, osteoarthritis, asthma, chronic obstructive pulmonary disease COPD, tissue fibrosis, eosinophilic inflammation, esophagitis, inflammatory bowel diseases (e.g. Crohn's, ulcerative colitis), transplantation, graft-versus-host disease, psoriasis, myositis, multiple sclerosis. (Kopf et al., 2010)
Osteoarthritis (also referred to as OA, or wear-and-tear arthritis) is the most common form of arthritis and is characterized by loss of articular cartilage, often associated with hypertrophy of the bone and pain. (Wieland et al., 2005)
Osteoarthritis is difficult to treat. At present, no cure is available and treatment focuses on relieving pain and preventing the affected joint from becoming deformed. Common treatments include the use of non-steroidal anti-inflammatory drugs (NSAIDs). Although dietary supplements such as chondroitin and glucosamine sulphate have been advocated as safe and effective options for the treatment of osteoarthritis, a recent clinical trial revealed that both treatments did not reduce pain associated with osteoarthritis. (Clegg et al., 2006)
Stimulation of the anabolic processes, blocking catabolic processes, or a combination of these two, may result in stabilization of the cartilage, and perhaps even reversal of the damage, and therefore prevent further progression of the disease. Therapeutic methods for the correction of the articular cartilage lesions that appear during the osteoarthritic disease have been developed, but so far none of them have been able to mediate the regeneration of articular cartilage in situ and in vivo. Taken together, no disease modifying osteoarthritic drugs are available.
Vandeghinste et al. (Vandeghinste et al., 2005) discovered JAK1 as a target whose inhibition might have therapeutic relevance for several diseases including OA. Knockout of the JAK1 gene in mice demonstrated that JAK1 plays essential and non-redundant roles during development: JAK1−/− mice died within 24 h after birth and lymphocyte development was severely impaired. Moreover, JAK1 −/− cells were not, or less, reactive to cytokines that use class II cytokine receptors, cytokine receptors that use the gamma-c subunit for signaling and the family of cytokine receptors that use the gp130 subunit for signaling. (Rodig et al., 1998)
Various groups have implicated JAK-STAT signaling in chondrocyte biology. Li et al. (Li et al., 2001) showed that Oncostatin M induces MMP and TIMP3 gene expression in primary chondrocytes by activation of JAK/STAT and MAPK signaling pathways. Osaki et al. (Osaki et al., 2003) showed that interferon-gamma mediated inhibition of collagen II in chondrocytes involves JAK-STAT signaling. IL1-beta induces cartilage catabolism by reducing the expression of matrix components, and by inducing the expression of collagenases and inducible nitric oxide synthase (NOS2), which mediates the production of nitric oxide (NO). Otero et al. (Otero et al., 2005) showed that leptin and IL 1-beta synergistically induced NO production or expression of NOS2 mRNA in chondrocytes, and that that was blocked by a JAK inhibitor. Legendre et al. (Legendre et al., 2003) showed that IL6/IL6 Receptor induced downregulation of cartilage-specific matrix genes collagen II, aggrecan core and link protein in bovine articular chondrocytes, and that this was mediated by JAK/STAT signaling. Therefore, these observations suggest a role for JAK kinase activity in cartilage homeostasis and therapeutic opportunities for JAK kinase inhibitors.
JAK family members have been implicated in additional conditions including myeloproliferative disorders (O'Sullivan et al., 2007), where mutations in JAK2 have been identified. This indicates that inhibitors of JAK in particular JAK2 may also be of use in the treatment of myeloproliferative disorders. Additionally, the JAK family, in particular JAK1, JAK2 and JAK3, has been linked to cancers, in particular leukaemias e.g. acute myeloid leukaemia (O'Sullivan et al., 2007; Xiang et al., 2008), and acute lymphoblastic leukaemia (Mullighan et al., 2009) or solid tumours e.g. uterine leiomyosarcoma (Constantineseu et al., 2008), prostate cancer (Tam et al., 2007). These results indicate that inhibitors of JAK, in particular of JAK1 and/or JAK2, may also have utility in the treatment of cancers (leukaemias and solid tumours e.g. uterine leiomyosarcoma, prostate cancer).
In addition, Castleman's disease, multiple myeloma, mesangial proliferative glomerulonephritis, psoriasis, and Kaposi's sarcoma are likely due to hypersecretion of the cytokine IL-6, whose biological effects are mediated by intracellular JAK-STAT signalling (Naka et al., 2002). This result shows that inhibitors of JAK may also find utility in the treatment of said diseases.
The current therapies are not satisfactory and therefore there remains a need to identify further compounds that may be of use in the treatment of allergic diseases, inflammatory diseases, autoimmune diseases, proliferative diseases, transplantation rejection, diseases involving impairment of cartilage turnover, congenital cartilage malformations, and/or diseases associated with hypersecretion of IL6 or hypersecretion of interferons. The present invention therefore provides compounds, methods for their manufacture and pharmaceutical compositions comprising the compounds of the invention together with a suitable pharmaceutical carrier. The present invention also provides for the use of a compound of the invention in the preparation of a medicament for the treatment of allergic diseases, inflammatory diseases, autoimmune diseases, proliferative diseases, transplantation rejection, diseases involving impairment of cartilage turnover, congenital cartilage malformations, and/or diseases associated with hypersecretion of IL6 or hypersecretion of interferons.